Alloy steel article



Patented Nov. 26, 1940 UNITED STATES PATENT OFFICE ALLOY STEEL ARTICLENo Drawing. Original application June 25, 1935,

Serial No. 28,374. Divided and this application October 19, 1937, SerialNo. 169,906

1 Claim.

This application is a division of my copending Application 28,374 filedJune 25, 1935 and entitled Alloy and manufactures, now Patent 2,125,929of August 9, 1938, and the invention relates to 5 chromium-nickel alloyirons and steels and to tubular articles and manufactures of the same.

Among the objects of my invention is the production of chromium-nickelalloy irons and steels which are strong, tough, durable and which arereadily workable, as by forging and rolling into plates, bars, sheet,strip, rods and wire, which may be further machined, worked or formed,as by drilling, cutting, turning and bending, which may be welded wheredesired, to achieve a great number of products, articles ormanufactures, such as tubing and piping, fluid valves, all for hightemperature duty, as in stills, evaporator units and the like, forsemi-chemical uses in the canning, dairy, oil and photographic filmindustries, or in chemical calciners used in the production of paintsand dyes, or like articles, products or manufactures for hightemperature service applications.

The invention accordingly consists in the combination of elements,composition of ingredients and mixture of materials, and in thearticles, products and manufactures of the same, as described herein,the scope of the application of which is indicated in the followingclaim.

certain features of my invention it may be noted at this point that theaustenitic chromium-nickel irons and steels (irons and steels containingapproximately, 10 to 25% chromium, 7% to 15% nickel, and the balancesubstantially iron) are used in the production of a wide variety ofcorrosion-resistant and mildly heat-resistant products or articles ofmanufacture. Thus, these austenitic irons and steels, especially the18-8 irons and steels (irons and steels containing 18% chromium, 8%nickel, and the balance substantially iron) may be used in a number ofinterior or exterior architectural applications, such as decorativetrim, ornamentation and fixtures. Likewise, these irons and steels maybe employed for a variety of kitchen, soda fountain, dairy and hospitalapplications, as in cooking and serving utensils, containers andappliances, counter and furniture trim and the like, where permanentlybright corrosion-resistant metal capable of withstanding the corrosiveaction of various fruit and vegetable acids, is desired. Similarly,these irons and steels are widely adapted for various chemical plantapparatus and equipment where metal resistant to the corrosive attack ofacids, alkalies As conducive to a clearer understanding of and salts atroom temperature, or slightly elevated temperatures, is required.

These austenitic chromium-nickel irons and steels, however, are notsatisfactorily adaptable to extremely high temperature duty, especiallyhigh temperature duty under strongly oxidizing or corrosive conditions,largely because of the susceptibility of these irons and steels tointergranular corrosion and because of their tending to flow at hightemperatures.

One of the outstanding objects of my invention is the production ofstrong, tough and ductile alloy irons and steels, which maybe readilyworked or formed into a variety of tubular products, ar-

.ticles or manufactures, which are resistant to scaling, pitting andintergranular corrosion or corrosion embrittlement, at high temperaturesover long periods of continuous operation under a variety of corrosiveor corrosion-fostering media and under the many varying conditions encountered in actual, practical use.

Referring now more particularly to the practice of my invention, alloyiron or steel analyzing approximately, 18% chromium, 8% nickel, 2.5% to3.5% tungsten, 1% to 2% molybdemun, .0'7% to .1% carbon, and the balancesubstantially iron, with the usual percentages of silicon, manganese,sulphur and phosphorus, is conveniently produced in an electric furnacein a suitable manner, as for example, as described in Patent No.1,925,182 granted to Alexander L. Feild September 5, 1933 and entitledProcess for the manufacture of rustless iron. The alloy iron or steel ofdesired analysis is poured into suitable ingot molds where it ispermitted to cool. The formed ingots are stripped from the molds andfashioned into blooms or billets in accordance with known methods andconveniently converted by hotworking methods or a combination of hot andcold methods into plate, sheet, strip, bars, r'ods or wire of desireddimensions. When .desired the converted products are annealed to relieveworking strains and then cooled all in accordance with known methods.The cold-rolled sheet and strip, however, is preferably used withoutbenefit of annealing treatment in order to gain full realization of thestrength, hardness and other superior physical characteristics impartedby the coldworking operations. 1

My alloy iron or steel is essentially austenitic in structure butcontains certain new constituents in the form of complex ferrites andcarbides lending to the metal superior working, corrosionresisting andphysical characteristics. The metal is corrosion-resistant andheat-resistant, withstanding the conditions of high temperature dutyover long periods of continuous use and under a wide variety ofcorrosive or corrosion-fostering media, including sulphur-bearing vaporsand gases, such as hydrogen sulphide, in addition to those agentsnormally present in the atmosphere, without general, local orintergranular corrosion, grain growth, fatigue or failure. For example,a bar of austenitic chromium-nickel iron analyzing approximately, 18%chromium, 8% nickel, 3% tungsten, 2% molybdenum, .10% carbon, and thebalance substantially iron, subjected to a stress of 8,000 pounds persquare inch at a temperature of 1500 F., under ordinary atmosphericconditions, has a life of about 600 hours. Ordinary 18--8 chromium, 8%nickel, .07% carbon, and the balance substantially iron, has a life ofonly about 12 hours under like conditions of operation.

My chromium-nickel alloy iron or steel, in addition to having a lifeunder high temperature operating conditions greatly in excess of heretoafore known and/or used chromium-nickel irons and steels, is strong,tough and ductile and readily lends itself to a variety of working andforming operations either from sheet, strip or bar stock. The metal maybe forged, upset or drawn, it may be hot or cold rolled into sheet,strip and bar stock, which may be further worked or formed, as bybending, punching or blanking and may be machined by drilling, cutting,

threading or the like, followed by welding where desired, either with,the oxy-acetylene torch or with the electric are (preferably employingwelding rods of approximately the same analysis as the stock welded) toachieve a great many tubular articles, products and manufactures. (Thevarious welded articles, products and manufactures are preferably givena stabilizing heattreatment in accordance with well known methods toestablish a stabilized condition of the metal after the welding iscompleted in order to assure minimum intergranular corrosion and maximumcorrosion resistance in use.) For example, the bar, sheet and stripworked or formed as above indicated is fashioned into tubes, fluidvalves, couplings, all for high temperature duty as in boilers,condensers, oil cracking stills, evaporator units and the like, or forsemi-chemical uses in the canning, dairy, oil and photographic filmindustries, or chemical calciners, as used in the production ofiron-free chemicals, such as paints and dyes.

Thus, it will be seen that there is provided in this invention achromium-nickel alloy iron or steel and articles, products andmanufactures of the same in which the various objects hereinbeforenoted, together with many thoroughly practical advantages aresuccessfully achieved. It will be seen that the alloy is strong, tough,

corrosion-resistant and heat-resistant and that it readily lends itselfto a variety of working or forming operations into a number ofcommercial tubular articles, products or manufactures, many of which areset forth above, which are especially adapted to withstand continuoushigh temperature and high pressure duty over long periods of time andunder the many varying conditions of actual, practical use, such as theWash and scour of corrosive fluids.

While as illustrative of my invention an austenitic chromium-nickel ironcontaining approximately, 18% chromium, 8% nickel, 2.5% to 3.5%tungsten, 1% to 2% molybdenum, .07% to.l% carbon, and the balancesubstantially iron, is specifically described, good results are achievedwherethe chromium content ranges between 10% and 25% and the nickelcontent between 7% and Similarly, chromium-nickel alloy irons or steelspossessing long life at high temperatures in combination with goodmechanical workability, are achieved where the tungsten content rangesfrom just above 2% up to about 4% and the molybdenum content ranges fromabout .'7% up to about 3%. Likewise, good high temperature dutycharacteristics are achieved in modified chromium-nickel alloy irons andsteels where the carbon content ranges between 03% and 2%.

Certain further benefits in long-like alloy iron and steel at unusuallyhigh operating temperatures are achieved by adding to thetungstenmolybdenum-chromium-nickel alloy iron or steel, the furtheringredient, manganese, in the amount of from about .5% to 3%. Hightemperature duty irons and steels of this analysis are especiallyresistant to the corrosive attack of sulphur-bearing gases at hightemperatures and are of somewhat improved workability over the hightemperature irons and steels indicated above.

As many possible embodiments may be made of my invention and as manychanges may be made in the embodiment hereinbefore set forth, it is tobe understood that all matter described herein is to be interpreted asillustrative, and not in a limiting sense.

I claim:

Wrought alloy austenitic 10 to 25 per cent chromium, 7 to 15 per centnickel and .03 to .20 per cent carbon, stainless steel tubular articlescharacterized by their freedom from corrosion embrittlement and by theirresistance to the wash and scour of corrosive fluids, used underconditions of high internal pressures and at high temperatures, saidcharacteristics being produced by the inclusion in said alloy steel of.7 to 3 per cent molybdenum and over 2 per

